Dual temperature refrigeration



July 16, 1957 A. E. SCHUBERT ETAL 2,799

DUAL TEMPERATURE REFRIGERATION Filed June 29, 1954 Fl'gj.

| [n ven 'ors Albert E. Schubert, Theodore L. .Etherington,

Their" Attorney United States Patent 2,799,142 DUAL TEMPERATURE REFRIGERATION Application June 29, 1954, Serial No. 440,027

6 Claims. (Cl. 623) This invention relates to refrigeration systems and specifically to a method and apparatus to secure dual temperature levels in such systems.

Refrigeration systems, which are capable of providing dual temperature levels, are desirable in heat pump construction and in commercial and domestic refrigerators. It is desirable to vary the temperature of a heat pump evaporator while reasonably constant suction pressure conditions are maintained at the compressor. Such temperature variance is not possible in a refrigeration system which employs only a single refrigerant.

Accordingly, it is-object of our invention to provide a new and improved refrigeration system in which a pair of different refrigerants are employed.

It is another object of the invention to provide a dual temperature refrigeration system which selectively circulates a particular refrigerant in response to the load upon the system.

It is another object of the invention to provide a refrigeration system which employs a batch distillation unit to purify the refrigerants.-

' It is a further object of the invention to provide a novel method of refrigeration in which a pair of different refrigera'nts. are selectively circulated to produce dual'temperature level refrigeration. v

In carrying out our invention in one form, a pair of different refrigerants are selectively circulated in a refrigeration system to provide dual temperature levels of refrigeration.

7 These and various other objects, features and advantages ofthe invention will be better understood fromfthe fol- A packed distillation column 28 connects reboiler 26 with a condenser 29 which is cooled in a similar manner to condenser 12. A tube 30 with a solenoid valve 31 is provided between the outlet of condenser 12 and reboiler 26 to circulate contaminated refrigerant to distillation unit 25. The purified refrigerants are returned to receivers 13 and 14 through a pair of tubes 32 and 33 with associated solenoid valves 34 and 35, respectively. A pressure equalizing tube 36 with a solenoid valve 37 connects condenser 29 with receiver 13. Batch distillation unit 25 is actuated by a product take-on control which is indicated generally at 40.

As it is best shown in Fig. 2, control 40 comprises a casing 41 in which a pair of opposed bellows 42 and 43 are separated by a plate 44. Bellows 42 communicates through a tube 45 with a bulb 46 which is filled with a mixture of refrigerants 21 and 22 of a desired composition. Bulb 46 is positioned in distillation column 28 to provide a purity control point. Bellows 43 is connected to condenser 29 through a tube 47 to provide a pressure tap. A steel spring 48 is mounted on one end of plate 44 to provide a lever which will actuate a micro switch 49. Micro switch 49 actuates solenoid valve 34 of the refrigeration system for purposes to be described hereinbelow.

The solenoid valves of the refrigeration system may be actuated by a sensing and sequencing control device (not shown), such as, for example, a temperature sensitive bimetal switch, which is sensitive to temperature variations. The switch initiates motion of a series of cams attached to a shaft which is driven through a gear box lowing description taken in connection with the accorn- {I panying drawing in which:

Fig. 1 is a schematic view of one form of a refrigeration system which embodies our invention; and

Fig. 2 is an enlarged sectional view of the product take-off control which is shown in Fig. 1.

In Fig. l of the drawing, a refrigeration system, which may be used in heat pump construction or in commercial or domestic refrigerators and which is indicated generally at 10, comprises a compressor 11 to communicate on its high pressure side with a condenser 12. Condenser 12 is connected to a pair ,of liquid receivers 13 and 14 through a pair of solenoid valves 15 and 16. Receivers 13 and 14 communicate with an evaporator 17 through a conventional expansion valve 18 which may be controlled by a pressure tube 19 and diaphragm 20. A temperatureoperated or thermostatic expansion valve or sections of capillary tubing may be employed as the expansion device. Different refrigerants 21 and 22 are contained in each of the receivers 13 and 14 whose outlets are controlled by solenoid valves 23 and 24, respectively. Evaporator i7 is connected to the inlet or low pressure side of compressor 11.

A batch distillation unit 25, which is provided in the refrigeration system to purify refrigerants 21 and 22, comprises a reboiler 26 with a heating unit 27 thereunder.

by a small motor to operate spring contacts to make and break the control circuits in proper sequence.

In the operation of the refrigeration system which is shown in Fig. 1 of the drawing, liquid receivers 13 and 14 are filled with different refrigerants 21 and 22, such as, for example, Freon 22 and Freon 12. If it is desired to circulate refrigerant 21 through the system, valves 15 and 23 are placed in an open position while valves 16, 24, 31, 34, 35, and 37 are closed. Compressor ll pumps refrigerant 21 through condenser 12 and valve 15 to receiver 13. Refrigerant 21 will then flow through valve 23, expansion valve 18, and evaporator 17 to compressor 11. A change in the load on the system actuates the sensing and sequencing device (not shown) to close valve 15 a nd1open valve 31. Refrigerant'zl will then flow from receiver 13 through valve 23, expansion valve 18, evaporator 17, compressor 11, condenser 12, tube 30 and valve 31 to reboiler 26. After refrigerant 21 has been circulated to reboiler 26 to substantially purge the system of refrigerant 21, the control device closes valves 23 and 31 and opens valves 16 and 24 to circulate refrigerant 22 through the refrigeration system. Refrigerant 22 will be pumped from compressor 11 through condenser 12 and valve 16 to receiver 14.

The control device opens valve 37 and actuates heating unit 27 to vaporize refrigerant 21 which rises in column 28 to condenser 29 where it is condensed. When the vapor of refrigerant 21 is of desired purity, its composition will be identical with the liquid mixture in bulb 46 of product control device 40. Pressure, which is transmitted to bellows 42, is the same as column pressure which is transmitted through tube 47 to bellows 43 while composition is identical in vapor and bulb liquid. When column pressure is equal to or greater than pressure exerted in bellows 42, lever 48 of plate 44 will engage micro switch 49 to operate solenoid valve 34 and allow essentially pure refrigerant 21 to flow through tube 32 to liquid receiver 13. When the composition of the vapor at bulb 46 becomes richer in refrigerant 22, the pressure in bellows 42 exceeds the column pressure in 37, and opens valve 35 to allow essentially pure refrigerant 22 to return to receiver 14.

When the load on the system chan es again, the control device closes valve 16 and opens valve 31 to circulate refrigerant 22 to the reboiler 26. After all of refrigerant 22 has been returned to reboiler 26, valve 31 closes and valves 15, 23 and 37 open. Heating unit 27 is activated to distill off any refrigerant 21 which is present in contaminated refrigerant 22. Refrigerant 21 will be vaporized, condensed, and returned to receiver 13 as in the previously described distillation of refrigerant 21. When essentially pure refrigerant 22 remains in reboiler 26, the control device inactivates heating unit 27, opens valve 35 to return refrigerant 22 to receiver 14 and closes valve 35. The refrigeration system will continue to operate on refrigerant 21 until the system load changes sufficiently to actuate the control device.

As will be apparent to those skilled in the art, the objects of our invention are attained by the use of a pair of different refrigerants which are separated and circulated selectively in a refrigeration system to provide dual temperature levels of refrigeration.

While other modifications of this invention and variations of apparatus which may be employed in the scope of the invention have not been described, the invention is intended to include all such as may be embraced within the following claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A method of refrigeration which comprises providing a pair of refrigerants in a refrigeration system, selectively circulating one of the refrigerants through the system, substantially purging the system of said one refrigerant, circulating the other refrigerant through the system, and purifying the one refrigerant during the circulation of the other refrigerant.

2. In a refrigeration system including :a compressor, a condenser, and an evaporator, a pair of refrigerants, means to purify said refrigerants, said purification means comprising a batch distillation unit, pressure responsive means to control said purification means, and valve means to circulate one of said refrigerants through the evaporator.

3. The invention as claimed in claim 2 wherein said sive to a first pressure in said system, a. second bellows responsive to a second pressure in said system, and control means associated with said first and said second bellows, whereby a difference in said first and said second pressures produces a differential movement of said bellows to operate said control means.

4. The invention as claimed in claim 2 wherein said pressure responsive means includes a first bellows responsive to a first pressure in said distilling means, a second bellows responsive to a second pressure in said distilling means, said first and said second bellows arranged for differential movement in response to said first and said second pressures, an electrical circuit making and breaking device associated with said first and said second bellows, whereby a pressure differential of said first and said second pressures produces a differential movement of said bellows to actuate said circuit maker and breaker.

5. In a refrigeration system including an evaporator, a compressor, a condenser, the combination comprising, a pair of storage receivers in said system, each of said receivers being adapted to supply a refrigerant to said system, a different refrigerant in each of said receivers, means to selectively circulate one of said refrigerants through said system to return to its receiver, distilling means arranged to receive a refrigerant from said system to purify the said refrigerant and return the said refrigerant to its receiver, and means to control the circulation of refrigerant to said distilling means.

6. In a refrigeration system, the combination comprising, a pair of storage receivers, a different refrigerant in each receiver, an evaporator arranged to receive a refrigerant from said receivers, a compressor arranged to receive a refrigerant from said evaporator, a condenser arranged to receive a refrigerant from said compressor and to re-circulate said refrigerant to the said receivers, means to selectively circulate one of said refrigerants through said system to return to its respective receiver, distillation means connected to said system between the evaporator and the storage receivers and arranged to receive a refrigerant thereby, and means to control the circulation of refrigerant to said distilling means, said means being responsive to the change in selection of refrigerant in said system to circulate the refrigerant in said system to the said distillation means for purification and return of the said refrigerant to its respective receiver.

References Cited in the file of this patent UNITED STATES PATENTS 1,904,326 Penn Apr. 18, 1933 2,037,155 Stewart Apr. 14, 1936 2,227,138 Newton Mar. 24, 1943 

